1. Field of the Invention
The present invention relates to a liquid crystal display device (LCD), and more particularly, to a LCD device of which a size and a weight are reduced.
2. Description of the Related Art
In recent times, information processing devices continue to rapidly develop with various architectures, functions and faster information processing speed. Information processed in these information processing devices has an electrical signal format. In order to visually confirm information processed in the information processing device, a display as an interface should be provided.
Recently, a LCD device that is lighter, and smaller than a CRT type display device has been developed. The LCD device has a full color displaying function and a high resolution. As a result, the LCD device is widely used as a monitor of a computer, a television, and another display device.
The LCD device applies a voltage to a predetermined molecular arrangement of a liquid crystal to convert the molecular arrangement to another molecular arrangement. The LCD device converts the changes of optical properties to visional changes and uses the modulation of a light by using a liquid crystal cell.
LCD devices are divided into to a TN (Twisted Nematic) type and a STN (Super-Twisted Nematic) type, and are also divided into an active matrix display type that uses a switching device and a TN liquid crystal and a passive matrix display type that uses a STN liquid crystal according to the driving type.
The active matrix display type is used in a TFT-LCD and drives an LCD by using a thin film transistor (TFT) as a switch. The passive matrix display type does not use any transistor and does not need a complex circuit.
Further, LCD devices are divided into a transparent LCD device that uses a backlight and a reflective LCD device that uses an exterior light source according to a method for using a light source.
The transparent LCD device that uses the back light as a light source has a heavy weight and a large volume due to the existence of the back light, but is widely used since it independently displays an image without using an exterior light source.
FIG. 1 is an exploded perspective view schematically showing a conventional LCD device 100. FIG. 2 is a sectional view showing a combination construction of the LCD device 100 shown in FIG. 1.
Referring to FIG. 1, the LCD device 100 has a LCD module 130 for displaying an image when an image signal is applied thereto and front and rear cases 110 and 120 for receiving the LCD module 130. The LCD module 130 includes a display unit 170 having a LCD panel for displaying the image and a backlight assembly 150 for supplying light to the display unit 170.
The display unit 170 includes a LCD panel 171, a data side printed circuit board 176, a gate side printed circuit board 175, a data side tape carrier package 178 and a gate side tape carrier package 174.
The LCD panel 171 has a TFT substrate 172, a color filter substrate 173 and liquid crystal (not shown).
The TFT substrate 172 is a transparent glass board on which the TFTs are formed in a matrix type. Data lines are respectively connected to source terminals of the TFTs and gate lines connected with gate terminals of the TFTs. Furthermore, pixel electrodes are respectively formed at drain terminals of the TFTs, which are comprised of a transparent conductive material such as Indium Tin Oxide (ITO).
The color filter substrate 173 faces to the TFT substrate 172. RGB pixels are formed on the color filter substrate 173 via a thin film process, which gives a predetermined color while the light passes through the color filter substrate 173. Common electrodes made of ITO are coated on the front surface of the color filter substrate 173.
When the TFTs of the TFT substrate 172 are turned on by applying electric power to the gate terminals and to the source terminals of the TFTs, an electric field is formed between the pixel electrodes of the TFT substrate 172 and the common electrodes of the color filter substrate 173. The electric field forces the liquid crystal, which is injected between the TFT substrate 172 and the color filter substrate 173, to change the array angle thereof, resulting in that the transmission of the light is changed. As a result, the desired pixels are obtained.
Meanwhile, a driving signal and a timing signal are applied to the gate lines and data lines of the TFT to control the array angle of the liquid crystal and the time of arraying the liquid crystal in the LCD panel 171. As shown in FIG. 1, the data side tape carrier package 178 that is comprised of flexible circuit boards, is attached to the source portion of the LCD panel 171 to decide a time of applying a data driving signal. On the other hand, the gate side tape carrier package 174 is attached to the gate portion of the LCD panel 171 to decide an application time of a gate driving signal.
The data side printed circuit board 176 and the gate side printed circuit board 175, which respectively apply the driving signal to the gate line and to the data line as soon as receiving image signals input from outside of the LCD panel 171, make contact with the data side tape carrier package 178 for the data line and the gate side tape carrier package 174 for the gate line in the LCD panel 171, respectively. A source portion is formed on the data side printed circuit board 176 to receive the image signals from an information process device (not shown) such as a computer, etc. and then to provide the gate driving signal for the gate line of the LCD panel 171 and a gate portion is formed on the gate side printed circuit board 175 to provide the gate driving signal to the gate lines of the LCD panel 171. That is, the data side printed circuit boards 176 and the gate side printed circuit board 175 generate and apply the gate driving signal and the data signal for driving the LCD device and a plurality of timing signals for applying the gate driving signal and the data signal to the gate lines and the data lines of the LCD panel 171, so as to provide the gate driving signal through the gate side tape carrier package 174 to the gate lines of the LCD panel 171 and to supply the data signal through the data side tape carrier package 178 to the data lines of the LCD panel 171.
The backlight assembly 150 is provided under the display unit 170 to uniformly supply the light to the display unit 170. The backlight assembly 150 includes lamp units 161 and 162, which are disposed at both ends of a LCD module 130, for generating the light, a light guide plate 152 for guiding the light emitted by the lamp units 161 and 162 toward the display unit 170 by changing a pathway of the light, a plurality of optical sheets 153 for uniformly making a brightness of the light which is transmitted from the light guide plate 152 and a light reflecting plate 154, which is provided under the light guide plate 152, for reflecting a leaked light to the light guide plate 152 so as to improve the efficiency of the light.
The display unit 171 and the backlight assembly 150 are successively received in a mold frame 132 used as a receiving container. The mold frame 132 is provided with a top chassis 140, which faces and is combined with the mold frame 132, for preventing the display unit 171 from departing from the mold frame 132.
Meanwhile, the LCD device further includes a power supply printed circuit board 135, which has an inverter circuit, for supplying the power source to the lamps of the lamp units 161 and 162 and a signal conversion printed circuit board 134 for converting and providing outer data signals to the data side printed circuit board 176.
The power supply printed circuit board 135 and the signal conversion printed circuit board 134 are fixed to a rear surface of the bottom chassis 131 by means of a bracket 133, as shown in FIGS. 1 and 2. Particularly, when the top chassis 140 is assembled with the mold frame 132 to form the LCD module 130, the LCD module 130 is received in the front case 110. The power supply printed circuit board 135 and the signal conversion printed circuit board 134 are combined to the rear surface of the bracket 133 by means of the screws 134c, 134d and 135b so that supports 134a, 134b and 135a are disposed between the rear surface of the bracket 133 and the power supply printed circuit boards 135 and the signal conversion printed circuit board 134. The bracket 133 is combined with the front case 110 by means of screws 133a and 133b.
Then, a shield case 136 is disposed at the rear surface of the bracket 133 to enclose the power supply printed circuit board 135 and the signal conversion printed circuit board 134. The shield case 136 insulates an electromagnetic wave generated form the LCD module 130 including the power supply printed circuit board 135 and the signal conversion printed circuit board 134.
As described above, when the bracket 133 and the shield case 136 are combined to the rear surface of the LCD module 130, the rear case 120 is coupled to the front case 110 and supported by the support 180 to complete the LCD monitor device (see FIG. 3).
As shown in FIG. 2, the power supply printed circuit board 135 and the signal conversion printed circuit board 134 are mounted on the rear surface of the LCD module 130 by the combination with the bracket 133 having a predetermined height. Further, the shield case 136 is coupled to the rear surface of the bracket 133 by means of the screws 136a and 136b.
In the conventional LCD device, there are many problems as follows.
Firstly, with reference to FIG. 2, the thickness t1 of the LCD device increases to the extent of the heights of the bracket 133 and the shield case 136 and the heights of the supports 134a, 134b and 134a for fixing the power supply printed circuit board 135 and the signal conversion printed circuit board 134 to the bracket 133. Particularly, a thickness t2 of a rear surface of the LCD device greatly increases due to the bracket 133 and the shield case 136 as shown in FIG. 4.
Secondly, since the power supply printed circuit board 135 and the signal conversion printed circuit board 134 are installed to be adjacent to both ends of the bracket 133, an area of the shield case 136 is excessively wide for covering them. Thus, the end portion of the LCD device is as thick as the center portion of the LCD device.
Thirdly, since the power supply printed circuit board 135 and the signal conversion printed circuit board 134 are placed at a position far away from the lamp units 161 and 162 and from the data side printed circuit board 176, as not shown in detail in drawings, there is a problem in that a line for supplying the power and a line for transferring the signals are longer. Furthermore, when the line for supplying the power and the line for transferring the signals are longer, it becomes difficult to include and to fix the lines to the LCD module 130 in a stable fashion.